1. Field of the Invention
This invention relates to apparatus and methods for controlled chemical reactions which occur on a membrane. More specifically, the invention relates to apparatus and methods for performing reactions between a nucleic acid in solution and nucleic acid bound to a membrane.
2. Related Art
Apparatus and methods for the performance of hybridization reactions between nucleic acids in solution and nucleic acids bound to a membrane are known in the art.
One type of such system is exemplified by the "TURBO BLOT" (TM) Filter Processing System from American BioNuclear of Emeryville, CA. The device consists of a pouch containing a plastic mesh sleeve which surrounds a membrane which has, for example, various DNA samples immobilized at various loci on the membrane. The plastic envelope has ports through which fluids may be introduced or expelled. The plastic pouch is oriented substantially vertically on a slanted face of the device, with the ports at the top of the pouch. Reactants are introduced into and removed from the pouch through one of the ports by a syringe. The entire pouch assembly is mounted on a metallic frame. The entire assembly has to be manually removed to be placed in a water bath. After the desired reaction has occurred, a washing solution is thereafter introduced through one of the ports, and the wash solution is forced out the pouch's other port by a vacuum source.
Such devices possess the disadvantage of complexity of operation, bulkiness and high cost of manufacture. The device also requires a large amount of expensive reactant in order to properly bathe the membrane within the plastic pouch. Furthermore, there is an inherent difficulty in administering and removing the reactants and washing fluids with syringes and vacuum pumps. Also, the handling of the flexible pouch assembly presents a danger to personnel working with this known device. Since many of the reactants involved in hybridization research are radioactive, the possibility of spillage of the radioactive reactant presents a danger not only to personnel. The possibility of spillage also endangers the continued purity of various other chemicals in the laboratory.
In another known device, a flexible plastic bag containing the membrane with various loci having immobilized target reactants is heat-sealed after addition of the probe reactant. Scissors are used to open the bag after the reaction. Although the method employing the plastic bag is far less expensive than the above-described device employing syringes, it does not solve the problems of the susceptibility to puncture or tearing, or of its attendant dangers when radioactive reactants are being used. The manipulation of the flexible bag and the use of scissors in procedures involving radioactive reactants are issues of special concern. Furthermore, although the plastic bag method results in a decrease in the amount of expensive probe reactant which has to be used, more of that probe reactant is used than is actually necessary for performing the reaction.
What is therefore needed is an apparatus and method for carrying out chemical reactions on membranes in which the apparatus is easy and safe to use, minimizes the necessity of manual contact with potentially radioactive or otherwise dangerous reactants, reduces the volume of reactants needed, and is inexpensive to manufacture and simple to use.